The invention described herein may be manufactured and used by or for the government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
The field of the present invention pertains to a fire protection apparatus and system for detecting and extinguishing sparks, flames, or fire. More particularly, the invention relates to a fire fighting system for detecting and extinguishing a spark, flame, or fire on a heat sensitive explosive object, which identifies, locates and relays vital information related to the particular endangered explosive object. The invention protects heat sensitive objects, regardless of how they are heated. Throughout the description of the present invention, explosive objects such as bombs and missiles are used to illustrate the use of the invention; however, the invention can be used to protect any heat sensitive object from detonation, thermal damage, explosion, or chemical release of hazardous materials.
To prevent fires, and the resulting loss of life and property, the use of flame detectors or flame detection systems are not only voluntarily adopted in many situations, but are also required by the appropriate authority for implementing the National Fire Protection Association""s (NFPA) codes, standards, and regulations. Facilities faced with a constant threat of fire, such as petrochemical facilities and refineries, semiconductor fabrication plants, paint facilities, co-generation plants, aircraft hangers, silane gas storage facilities, gas turbines and power plants, gas compressor stations, munitions plants, airbag manufacturing plants, and so on are examples of environments that typically require constant monitoring of potential fire hazard situations.
An environment in which shipboard ordnances were exposed to the threat of detonation occurred on Jul. 29, 1967 on the nation""s first carrier, the USS Forrestal. The U.S. Navy was conducting combat operations off the coast of North Vietnam in the Tonkin Gulf on Yankee Station. A Zuni rocket accidentally fired from a F-4 Phantom on the starboard side of the ship into a parked and armed A-4 Skyhawk. The accidental launch and subsequent impact caused the 400 gallon belly fuel tank and a 1,000 pound bomb on the Skyhawk to fall off. The tank broke open spilling JP5 (jet fuel) onto the flight deck and ignited a fire. Within 90 seconds the bomb was the first to cook-off and explode, causing a massive chain reaction of explosions that engulfing half the airwing""s aircraft, and blew huge holes in the 3xe2x80x3 thick steel flight deck. Fed by fuel and bombs from other aircraft armed and ready for the coming strike, the fire spread quickly and many pilots and support personnel were trapped and burned alive. Fuel and bombs spilled into the holes in the flight deck igniting fires on decks further into the bowels of the ship. The crew heroically fought the fire and carried armed bombs to the side of the ship to throw them overboard for 13 hours. Once the fires were under control, the extent of the devastation was apparent. Most tragic was the loss to the crew: 134 had lost their lives, while an additional 64 were injured.
A fire on the flight deck of an aircraft carrier can quickly become catastrophic due to various types of stored explosive items and heat sensitive objects aboard. The firefighting crew, although highly trained and motivated to control and extinguish the conflagration, can be quickly eliminated in such a scenario because of their proximity to the detonating weapons that cook-off in the fire. This leaves less experienced, and less trained, trying to fight an extremely dangerous fire. It should be noted that a fire is not necessary in order to create a severe fire hazard or explosion in an industrial or military environment. An example of this comes from another aircraft carrier tragedy aboard the USS Enterprise (CVN-65), Jan. 14, 1969. This time, no fire existed prior to the start of weapons cooking-off. Rather, a Zuni rocket, loaded for combat on an F-4 Phantom, was heated until it exploded when the turbine exhaust from an aircraft starter unit (called a xe2x80x9chufferxe2x80x9d) was inadvertently positioned to blow directly on the weapons warhead. Subsequently, fire broke out when to damaged fuel tanks leaking fuel onto the deck ignited, causing the tragic death of 27 sailors.
Three primary contributing factors to a fire are: (1) fuel (such as JP5 aboard the USS Forrestal); (2) heat derived from jet exhaust or sympathetic detonation; and (3) oxygen. When the fuel is heated above its ignition temperature (or xe2x80x9cflash pointxe2x80x9d) in the presence of oxygen, a fire will occur. A fire can self-extinguish if one of the three above mentioned factors is reduced or eliminated. Thus, when the fuel supply of the fire is cut off, the fire typically stops. When a fire fails to self-extinguish, current fire protection systems incorporate flame detectors which are expected to activate suppression agents to extinguish the fire and thereby prevent major damage. It must be noted that the extinguishment of a fire does not remove the explosion hazard when certain industrial and military chemical compounds (such as explosives and propellants) have been heated by the fire that was extinguished. Under such conditions a phenomena known as xe2x80x9cthermal runawayxe2x80x9d can occur and an explosion can happen even after the device (weapon) has been removed from the fire and cooled. Once a complex chemical compound (like explosives or propellants) reaches its point-of-no-return, no amount of cooling can prevent it from cooking-off. In such cases, it is imperative to know the heating history of the compound in order to gauge when it will explode.
Flame detectors must meet standards set by the NFPA, which are becoming increasingly stringent. Thus, increased sensitivity, faster reaction times, and fewer false alarms are not only desirable, but are now a requirement. Previous flame detectors have many drawbacks. The drawbacks of these previous devices have led to false alarms, which unnecessarily stop production or activate fire suppression systems when no fire is present.
One drawback of the most common types of flame detectors is that they can only sense radiant energy in one or more of either the ultraviolet, visible, near band infrared (IR), or carbon dioxide (CO2) 4.3 micron band spectra. Such flame detectors tend to be unreliable and can fail to distinguish false alarms, including those caused by non-fire radiant energy sources (such as industrial ovens), or controlled fire sources that are not dangerous (such as a lighter). Disrupting an automated process in response to a false alarm can, as noted, have tremendous financial setbacks.
Another drawback of previous fire detectors is their lack of reliability, which can be viewed as largely stemming from their approach to fire detection. The most advanced fire detectors available tend to involve simple microprocessor controls and processing software of roughly the same complexity as those used for controlling microwave ovens. The sensitivity levels of these previous devices are usually calibrated only once, during manufacture. However, the sensitivity levels often change as time passes, causing such conventional flame detectors to fail to detect real fires or to false alarm. In addition, previous fire detectors require a continual source of energy to maintain the fire detection capabilities.
Many of the conventional flame detectors are limited by their utilization of pyroelectric sensors, which only detect the change in radiant heat emitted from a fire. Such pyroelectric sensors depend upon temperature changes caused by radiant energy fluctuations, and are susceptible to premature aging, degraded sensitivity and instability with the passage of time. In addition, such pyroelectric sensors do not take into account natural temperature variations resulting from environmental temperature changes that typically occur during the day, as a result of seasonal changes or prevailing climatic conditions.
Other types of conventional flame detectors identify fires by relying primarily on the ability to detect a unique narrow band spectral emissions radiated from hot CO2 fumes produced by the fire. Hot CO2 gas from a fire emits a narrow band of radiant energy at a wavelength of approximately 4.3 microns. However, cold CO2 (a common fire suppression agent) absorbs energy at 4.3 microns, and can therefore absorb a hot CO2 spike emission generated by a fire. In such situations, conventional CO2-based flame detectors can miss detecting a fire.
Another type of conventional IR flame detector monitors radiant energy in two infrared frequency bands, typically the 4.3 micron frequency band and the 3.8 micron frequency band, while others use as many as three infrared frequency bands. The dual IR frequency band flame detector commonly utilizes an analog signal subtraction technique for subtracting a reference sensor reading at approximately 3.8 microns from the sensed reading of CO2 at approximately 4.3 microns. The triple IR frequency band flame detector uses an analogous technique, with an additional reference band at approximately 5 microns. These types of multi-band flame detectors can produce a false alarm when cold CO2 obscures the fire source between the flame detector, thereby misleading the detector into believing that a strong CO2 emission spike from a fire is detected, when, in fact, a negative absorption spike (caused by e.g., a CO2 suppression agent discharge or leak) has been detected.
Conventional flame detectors using ultraviolet (xe2x80x9cUVxe2x80x9d) sensors also exist, but these have drawbacks as well. Also, because arc welding produces copious amounts of intense ultraviolet energy which can be reflected or transmitted over long distances, UV flame detectors can generate false alarms from such UV energy sources, even when the non-fire UV energy is located at a far distance from the spray booth. Moreover, after deployment, conventional UV detectors eventually can become highly de-sensitized as a result of absorbing smoke from a fire and/or solvent mist, causing the UV detector to become blinded. As a result, UV detectors can provide a false sense of security that they are operating at their optimum performance levels, when, in fact, the facility can be vulnerable to a costly fire.
As an additional disadvantage, UV flame detectors generally require a relatively clean viewing window lens for the UV sensor, and can therefore become blinded or degraded by the presence of paint or oil contaminants on the viewing window lens. Moreover, the sensing techniques utilized with conventional UV detectors usually do not take into account the effects of such types of lens degradation.
In addition to problems with flame detection, many or all-conventional flame detectors have limitations or drawbacks relating to their housing and/or mounting that can affect their performance or longevity, and are being relatively expensive to manufacture. For example, most optical flame detectors have been built with a metal housing made from costly aluminum, stainless steel, or similar materials. Such housings can be heavy, difficult to mount and may not be suitable for certain corrosive environments such as xe2x80x9cwet-benchesxe2x80x9d used in semiconductor fabrication facilities for manufacturing silicon chips and the like.
Further, most or all optical flame detector housings require a window lens (necessary for high optical transmission in the spectral bands used, and are typically made of glass, quartz, sapphire, etc.), but it is usually quite difficult to obtain a tight seal of the window lens to metal housings, particularly in chemical manufacturing, or integrated circuit manufacturing or other applications having extremely rigorous environmental requirements. When the flame detector is not tightly sealed, then corrosive chemicals can leak into the electronic circuitry and degrade or destroy the optical flame detector and housing.
In flame detectors that detect UV energy, the protective window lens must be constructed from highly expensive quartz, sapphire, or other similar material that does not block UV energy.
Moreover, the quartz or sapphire window lenses are typically placed in a metal detector housing which collect dust and contaminants due to the electrostatic effect of the high voltage field (around 300 to 400 volts) used in the UV detectors. To ensure that the UV detector""s sensor(s) can xe2x80x9csee throughxe2x80x9d the window lens, complex and costly xe2x80x9cthrough the lensxe2x80x9d tests are necessary. To conduct built-in xe2x80x9cthrough the lensxe2x80x9d window lens tests, a UV source tube is generally required to generate a UV test signal. Such UV source tubes require a high voltage for gas discharge sources and/or a large current for incandescent sources. Also, UV source tubes are subject to high failure rates. In sum, these self-tests are expensive, require extra power and space, and are prone to breakdowns. It should be noted that the term xe2x80x9cfire detectorxe2x80x9d includes other detectors, such as flame detectors and heat detectors, in the present text and refers generally to any process and/or system for detecting sparks, flames, heat or fires, including that produced by explosive type bombs, missiles, or other dangerous high-energy phenomena.
There is a need for a sensitive, reliable, automated, relatively inexpensive, intelligent, and effective method and system for detecting and extinguishing sparks, flames, or fire which limits the life threatening activity of firefighters and prevents tragedies like the one that occurred on the USS Forrestal.
The present invention relates to an automated fire protection apparatus and system. Overall, it provides the system parts needed to become aware that a hazardous event exists and manages the hazardous situation to minimize damage to property and life. A preferred embodiment of the present invention discloses a fire fighting protection system. First, the fire protection system includes a means for detecting thermal radiation emitted by a heat source, which also acts as a source of thermal energy. Next, a means for converting the thermal energy from the heat source to electrical energy is either a thermopile or a thermal battery, or both. A means for storing the electrical energy (preferably a capacitor) can be utilized with either a thermopile or optionally with a thermal battery. A thermopile is a thermoelectric device designed to convert a temperature gradient to electrical energy. It essentially uses a series of thermocouple beads to generate voltage. Each thermocouple bead is a junction of dissimilar metals that take advantage of the Peltier Effect. When the thermocouples are connected in series, every other thermocouple are exposed to hot temperatures (and those between the hot junctions exposed to cold temperatures), the effect is that of connecting a bunch of little electrical cells (batteries) in series. The voltage and current response of the thermopile can be manipulated as needed by arranging the thermocouples in arrays of series and parallel loops. The series loops contribute voltage, and the parallel loops contribute current.
The storing means or converting means charges to a specified level initiates a temperature sensor and a transmitter. The transmitter generates a data signal to a means for generating and communicating the data signal according to output from the transmitter. A means for receiving data signals from said transmitter is preferably a receiver and receiver antenna. The means for generating and communicating a signal transmits an omni-directional beacon emitted from the transmitter and produces a location signal. The means for accurately locating the transmitter preferably includes a beacon locator. Additionally, a means for analyzing the location signal and triangulates the location of the heat source(s) preferably is processed by a centralized control system.
A preferred embodiment of the present invention discloses a fire protection apparatus for detecting and responding to a fire. The fire protection apparatus includes a thermal radiation detector, a power supply subsystem converters, (capacitor and/or thermal battery), transmitter, data signal generator and communicator, and at least one location sensor. A thermal radiation detector senses thermal radiation emitted by a heat source, which also acts as a source of thermal energy. A power supply subsystem provides power to the apparatus. In a preferred embodiment, the power supply subsystem comprises a thermal energy to electrical energy converter and a capacitor. A thermal energy to electrical energy converter, such as a thermopile, converts the thermal radiation emitted by the heat source to electrical energy. A thermopile is a device that uses the Peltier effect to generate electrical voltage/current from a temperature difference, or an externally-heated-thermal-battery, a device that generates voltage and current by a chemical reaction that takes place at elevated temperatures. The electrical energy can be stored in an electrical energy storage device (such as a capacitor) at a specified level and then initiate at least one temperature sensor and a transmitter that generates a data signal. When a thermal battery is used as the power supply subsystem it generates voltage and at a specified level, the thermal battery initiates at least one temperature sensor and transmitter that generates a data signal. Charging the capacitor is optional for the thermal battery. A data signal generator and communicator transmit the data signal according to output from the transmitter. At least one beacon locator detects an omni-directional beacon emitted from the transmitter and produces a location signal and a location signal analyzer triangulates a position of each heat source.
Another preferred embodiment of the present invention is a sensor and transmitter device for a fire protection system including at least one status sensor for sensing thermal energy and producing a data signal, at least one converter for converting the thermal energy to electrical energy, at least one controller to process the data signals, at least one encoder to covert input from each the status sensor to a digital output and wherein the digital output is sent to the transmitter, and at least one transmitter for transmitting the data signal from the encoder. The converter is preferably, a thermopile or thermal battery. The controller is preferably a data processor, and the encoder is preferably an RF data link. The apparatus further includes an electrical storage means being a capacitor which is charged by the thermopile or thermal battery
An object of a preferred embodiment of the present invention is to provide an inexpensive, durable heat detector that continuously senses the temperature of the heat sensitive object that the present invention is protecting. This detector is mounted upon or within the object being protected and travels with it at all times. In another embodiment, the detector is removable.
Another object of a preferred embodiment of the present invention is to provide an inexpensive, durable encoder and transmitter that sends the output of the heat detector to an automated, computer-based firefighting control system across the hostile environment presented by burning fuel using electromagnetic waves.
Another object of a preferred embodiment of the present invention is to provide an automated, computer-based firefighting control system that interfaces with all vulnerable heat sensitive objects being protected, firefighting components and human operators, so that the system could run autonomously.
Another object of a preferred embodiment of the invention is to provide a mounted, fixed detector/sensor system that is able to locate the object being protected and determine its temperature, heating rate, composition and serial number using inputs from multiple detectors to triangulate actual explosive item(s) location.
A further object of a preferred embodiment of the invention is to provide automated turret-type fire fighting agent applicators and other automated (robotic) firefighting aids that will address the specific concerns and hazards of a given military or industrial environment. These are controlled by the control system to put a cooling stream of water or other agent onto the object of concern, or otherwise eliminate the fire and explosion hazard.
Ordnance-mounted Temperature Sensor Features:
Powered by a thermal energy to electrical energy converter or a thermal battery
Determines current temp and heat up rate
Outputs RF communications signals that may encode:
Weapon
Configuration (mark/mod)
Authentication
Temp of detector
Calculated heat up rate
Calculated total flux absorbed
Fastxe2x80x94actingxe2x80x94fast response turrets
Survives in fuel fire and functions reliably long enough to transmit its information to the sensing and locating system and monitor the thermal response of the item to which it is affixed, preferably up to 30 minutes or more.
Ordnance-mounted Power Supply Features:
Converts thermal energy from fire to electrical energy
Provides stable, metered DC output for electronics
Powers temp sensor electronics and transmitter
Small, light, and pliable (conforms to exterior of object to be protected, i.e. a weapons case)
Powers electronics for up to 30 minutes or more from brief exposure to fire
Ordnance-mounted Communications System Features:
Powered by a thermal energy to electrical energy converter or a thermal battery
Transmits data from temp sensor at specified time and/or temperature intervals
Powers transmit antenna
Antenna tuned to operate at elevated temperatures
Transmitter self-tunes output to maximize antenna gain at current antenna temperature
Low powerxe2x80x94draws mWsxe2x80x94transmits mWxe2x80x94high efficiency
Survives fuel fire and transmits reliably for  greater than 30 minutes through fire
Uses communication method clear of potential interference from fire
Uses communication method clear of other electromagnetic spectrum users
Hazards of electromagnetic radiation to ordnance (HERO)xe2x80x94safe
Sensing and Locating System (Centralized Control System):
Determines transmitting weapon and configuration (mark/mod)
Triangulates exact weapon location
Determines weapons temperature and heat up rate
Calculates time to cook-off
Expandable to control semi-autonomous fire fighting robotics such as automated turrets and/or sacrificial cooler